I have a good catamarandinghy as a candidate, but need a torqeedo electric to test with. Someone in my marina has a torqeedo, so I will see if they will let me barrow it for a bit of testing.

As efficient as your hull design is, and weight, I can guarantee your speed will be what ever the stock prop is. The stock prop is the V19 which is their way at hinting at what the pitch is without telling you. 19 means 19 kmph at 1300 rpm prop speed. By doing this, slip is an unknown but is clearly less than a prop spinning much faster on a gasoline outboard. 19 kmph = 11.5 mph or 10 kt. So on your efficient hull you will get that speed with either the 2.0 or 4.0 with the standard prop. What is unknown is the current draw, and should it be low, then you might be able to run the optional V30 prop which would give you a top speed of 16 kt. Since the display gives wattage, it will be easy to calculate if you can use the V30 prop. Another nice feature of the display is the remaining range at current speed is calculated on cumulative wattage useage, not battery voltage because lithium batteries have a almost flat voltage discharge curve. The display is user programmable so that if you decide to save money and roll your own lithium battery bank you just enter the capacity of your battery.

It is almost like you have been reading my posts over the years. You and I are proposing the same, a lighter weight per kw DC gen set vs a AC gen set that is frequency dependent for rpm. For a 60 cycle AC gen set, it would need to run at 1800 rpm, quiet and long lasting at that rpm, but larger and heavier for the same output of a DC gen set running at 2900 rpm. With a inverter, having that heavy AC gen set is redundant.

Whole different animal than the 2.0 and 4.0. Standard prop is a V9 so 4.75 kt. Input power is 1000 watts, so if your cat dinghy can reach 4.75 kt on that power, it should reach prop pitch speed on the 2.0. Still a guess if it can run 16 kt on the 4.0 and V30 prop.

My 6 hp gas engine pushes the dinghy cat to 12knots with 400lbs added.
Thats going into a 20 knot sea chop. It cuts through chop like it's not even there. And you stay dry while your doing it as all the chop stays in the tunnel.

My 6 hp gas engine pushes the dinghy cat to 12knots with 400lbs added.
Thats going into a 20 knot sea chop. It cuts through chop like it's not even there. And you stay dry while your doing it as all the chop stays in the tunnel.

Then I would say a 4.0 and the V30 prop would push your boat to 16 kt or really close so that the V30 would be the proper pitch for your boat. That speed you attained in those conditions with just 6 hp gas says the hull just slices through the chop and the wetted surface is minimal, good design, perfect for electric propulsion. Since you designed and built your cat, I'll bet you could find a nifty way to place the cells down in the Vee of the hulls.

Geez, you got me excited about your cat dinghy. Just tossing numbers out, it looks like you could slow cruise at 8 kt or so and only consume 200 w-hr per nm. (16) 200 a-hr LiFePO4 cells, 8 in each hull could give a range of 50 nm. That is cool, but if 256 lbs of cells is too much weight, then (16) of the 40 a-hr cells is only 53 lbs, good for 10 nm. A lot of choices in between those capacities. Winston cells come in these sizes, 40, 60, 90, 100, 160, 200, 260, 300, 400, 700, 1000 a-hr.

Geez, you got me excited about your cat dinghy. Just tossing numbers out, it looks like you could slow cruise at 8 kt or so and only consume 200 w-hr per nm. (16) 200 a-hr LiFePO4 cells, 8 in each hull could give a range of 50 nm. That is cool, but if 256 lbs of cells is too much weight, then (16) of the 40 a-hr cells is only 53 lbs, good for 10 nm. A lot of choices in between those capacities. Winston cells come in these sizes, 40, 60, 90, 100, 160, 200, 260, 300, 400, 700, 1000 a-hr.

256 lbs of cells is not a problem.
I wish I had someone take a picture of us from the dock when we took off and planed with four large people on board the cat.

At full throttle my inflatable would just barge and a wave of water would just soak everyone and we would get maybe 4 knots with four people. It truely sucked.

Four miles is the most we have ever done in our dinghy in the last 15 years.
Our FP Mahe 36 cat gets us very close to where we want to be. We love to explore in our dinghy also, but that stays in that 4 mile range.

Fifty miles would only be on the big cat with 4 miles at most on the small cat.

Four miles is the most we have ever done in our dinghy in the last 15 years.
Our FP Mahe 36 cat gets us very close to where we want to be. We love to explore in our dinghy also, but that stays in that 4 mile range.

Fifty miles would only be on the big cat with 4 miles at most on the small cat.

That gives you a lot of speed options vs battery capacity. With the 60 a-hr cells you could be full speed all the time if 8 to 10 miles is all the round trip range you need. Your boat would be worthy of a write up in a marine publication, zipping along at 16 kt on flowing electrons.

BTW, it was one of the entrants of this race that has shared with me that the Torqeedo motor and controller will accept up to 65 volts. He runs (18) LiFePO4 cells instead of the stock (16) cells, thus speed is higher by 11%.